The present invention relates to an apparatus for accelerating abrasive material with an impeller rotatably drivable about a rotation axis and comprising blades extending substantially radially to the rotation axis and a lateral disk to which the blades are connected along their side edges, as well as at least one feed line for feeding abrasive material, the outlet end of the feed line being at a spacing from the rotation axis of the impeller and bordering on the free side edges of the blades of the impeller.
In a known apparatus of this type described in U.S. Pat. No. 2,363,437, the abrasive material is fed into the working region of the blades of the impeller from the side. The blades are, in this connection, connected along a respective side edge to the lateral disk on which the drive elements of the impeller operate, while the other or free side edge of the blade passes by the outlet opening of the feed line for the abrasive material as the impeller rotates. This type of feeding-in of the abrasive material to the impeller can lead to damage, especially of its blades, if the fed-in abrasive material comprises large debris such as nuts or bolts, as the passage of the blades by the outlet opening of the feed line creates a “pinch angle” which is smaller, or, respectively, less, than such debris pieces. Furthermore, during the passage of the blades by the outlet opening, the inlet flow of the abrasive material into the impeller is interrupted for a short time.
In another known apparatus, disclosed in DD 265 847 A1, the abrasive material is fed into the impeller at the region at which the ends of the blades border on the hub. For this reason, the outlet opening of the feed line, which is formed as a sloped channel, extends into the working region of the blades, which themselves have correspondingly formed inner ends for passage by the outlet opening of the feed line. This manner of feeding-in the abrasive material into the interior of the impeller exhibits the same disadvantages as occur in connection with the known apparatus disclosed in U.S. Pat. No. 2,363,437, in that the passage of the blades by the channel-type outlet opening of the feed line creates, in any event, a “pinch angle”.
The challenge of the present invention is to provide an apparatus for accelerating abrasive material to which can be fed abrasive material comprising foreign objects which are larger than the abrasive material, without causing break damage of the impeller.